Revealing mistake: During Jack's dance scene, the old lady that he dances with spins away from him and knocks off a man's toupee. The actress was supposed to knock it off as she went by, but it's obvious that she misses and instead quickly reaches over to snatch it off his head instead.ksc
Other mistake: In the Regal Beagle, Jack addresses Marsha as Ms. White although later in the episode her last name is revealed to be Whitewood. In addition, how could Jack have known her last name anyway? Marsha only said her first name in front of Furley and the trio early in the episode and presumably she hasn't talked to the trio since she left with Furley out the door.
Character mistake: The whole idea of the serenading scene was Larry was supposed to hide and sing for Jack while Jack would be shown in the yard alone and pretend to be the one singing, but the yard was brightly lit and Larry was right behind Jack and both were very shown with nothing to hide Larry.
Factual error: In this episode, Jack asks Felipe how he can bring Mr. Angelino to The Apartment, in which he answers "We took the Santa Monica freeway to the Cloverfield exit." The Cloverfield exit is in reality, a good 2 miles or so from the beach (2 other exits are much closer to beach than this). Yet throughout the series, it is implied that The Apartment is very close to the beach (3 blocks is stated by Jack in a much earlier episode). Why a far exit for a beach-area apartment?